Imaging lens, camera and personal digital assistant

Abstract

An imaging lens includes in order from an object side a first lens group including a positive refractive power and a second lens group having a negative refractive power, the first lens group and the second lens group including a widest air space therebetween, the first lens group including in order from the object side a negative first lens having a concave face on the object side, a positive second lens having a convex face on both sides, an aperture stop, a negative third lens having a concave face on the object side, a positive fourth lens having a convex face on an image side and a positive fifth lens having a convex face on the image side, and the second lens group including a negative meniscus sixth lens having a concave face on the object side.

What is claimed is: 
     
       1. An imaging lens, comprising: in order from an object side
 a first lens group including a positive refractive power; and 
 a second lens group having a negative refractive power, 
 the first lens group and the second lens group including a widest air space therebetween, 
 the first lens group including in order from the object side a negative first lens having a concave face on the object side, a positive second lens having a convex face on both sides, an aperture stop, a negative third lens having a concave face on the object side, a positive fourth lens having a convex face on an image side and a positive fifth lens having a convex face on the image side, and 
 the second lens group including a negative meniscus sixth lens having a concave face on the object side. 
 
     
     
       2. The imaging lens according to  claim 1 , wherein a distance L from a most object-side face of the first lens group to an image face in a state focused on an infinite object and a focal length f of an entire system in a state focused on an infinite object satisfy the following condition (1):
   1.2< L/f< 2.0  (1).
 
 
     
     
       3. The imaging lens according to  claim 2 , wherein the focal length f of the entire system in a state focused on an infinite object and a maximum image height Y′ satisfy the following condition (2):
   0.50< Y′/f< 0.70  (2).
 
 
     
     
       4. The imaging lens according to  claim 1 , wherein a distance L from a most object-side face of the first lens group to an image face in a state focused on an infinite object and a distance D 1G-2G  from a most image-side face of the first lens group to a most object-side face of the second lens group in a state focused on an infinite object satisfy the following condition (3):
   0.15< D   1G-2G   /L< 0.50  (3).
 
 
     
     
       5. The imaging lens according to  claim 1 , wherein a focal length of the second lens group f 2G  and a focal length f of an entire system in a state focused on an infinite object satisfy the following condition (4):
   −2.7< f   2G   /f<− 1.2  (4).
 
 
     
     
       6. The imaging lens according to  claim 1 , wherein a curvature radius R L3F  of an object-side face of the third lens and a distance D L2-L3  from an image-side face of the second lens to an object-side face of the third lens satisfy the following condition (5):
   −2.5< R   L3F   /D   L2-L3 <−1.0  (5).
 
 
     
     
       7. The imaging lens according to  claim 1 , wherein a synthetic focal length f L1-L2  of the first and second lenses and a focal length f of an entire system in a state focused on an infinite object to satisfy the following condition (6):
   1.0< f   L1-L2   /f< 1.8  (6).
 
 
     
     
       8. The imaging lens according to  claim 1 , wherein the fifth lens includes as an image-side face an aspheric shape in which a positive refractive power weakens in its peripheral portion. 
     
     
       9. The imaging lens according to  claim 8 , wherein a distance L s-A  from the aperture stop to the aspheric surface of the fifth lens and a distance L s-I  from the aperture stop to the image face satisfy the following condition (7):
   0.25< L   S-A   /L   S-I <0.55  (7).
 
 
     
     
       10. The imaging lens according to  claim 1 , wherein the first lens is only moved when focusing on a close-range object. 
     
     
       11. A camera comprising the imaging lens according to  claim 1  as a photographing optical system. 
     
     
       12. A personal digital assistant comprising the imaging lens according to  claim 1  as a photographing optical system of a camera function portion.